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At least 109 records · Page 6

Simplified procedures for designing adhesively bonded composite joints

Procedures for the preliminary design of composite adhesive joints are described. Typical joints, their respective free body diagrams, and approximate equations for estimating the stresses in each of these typical joints are summarized. Equations are also presented to check the critical conditions of the joint such as minimum length, maximum adhesive shear stress, and peel-off stress. To illustrate the procedure, sample designs are described in step-by-step fashion for a butt joint with single doubler subjected to static loads, cyclic loads, and environmental effects. The results show that unsymmetric adhesive joints are inefficient and should be avoided, and hygrothermal environments and cyclic loads dramatically reduce the structural integrity of the joint and require several joint lengths compared with those for static load with no environmental effects.

Chamis, C. C.↗

Simplified procedures for designing adhesively bonded composite joints

Procedures for the preliminary design for composite adhesive joints are described. Typical joints, their respective free body diagrams, and approximate equations for estimating the stresses in each of these typical joints are summarized. Equations are also presented to check the critical conditions of the joint such as minimum length, maximum adhesive shear stress, and peel-off stress. To illustrate the procedure, sample designs are described in step-by-step fashion for a butt joint with single doubler subjected to static loads, cyclic loads, and environmental effects. The results show that unsymmetric adhesive joints are inefficient and should be avoided, and hygrothermal environments and cyclic loads dramatically reduce the structural integrity of the joint and require several joint lengths compared with those for static load with no environmental effects.

Chamis, C. C.↗

Validating a large geophysical data set - Experiences with satellite-derived cloud parameters

The goal of this study is to validate the global cloud parameters derived from the satellite-borne HIRS2 and MSU atmospheric sounding instrument measurements, and to use the analysis of these data as one prototype for studying large geophysical data sets in general. The HIRS2/MSU data set contains a total of 40 physical parameters, filling 25 MB/day; raw HIRS2/MSU data are available for a period exceeding 10 years. Validation involves developing a quantitative sense for the physical meaning of the derived parameters over the range of environmental conditions sampled. This is accomplished by comparing the spatial and temporal distributions of the derived quantities with similar measurements made using other techniques, and with model results. The need to work with Level 2 (point) data, rather than Level 3 (gridded) data for validation purposes is discussed, and some techniques developed for charting the assumptions made in deriving an algorithm and generating a code to produce geophysical quantities from measured radiances are presented.

Kahn, Ralph↗

Validating a large geophysical data set: Experiences with satellite-derived cloud parameters

We are validating the global cloud parameters derived from the satellite-borne HIRS2 and MSU atmospheric sounding instrument measurements, and are using the analysis of these data as one prototype for studying large geophysical data sets in general. The HIRS2/MSU data set contains a total of 40 physical parameters, filling 25 MB/day; raw HIRS2/MSU data are available for a period exceeding 10 years. Validation involves developing a quantitative sense for the physical meaning of the derived parameters over the range of environmental conditions sampled. This is accomplished by comparing the spatial and temporal distributions of the derived quantities with similar measurements made using other techniques, and with model results. The data handling needed for this work is possible only with the help of a suite of interactive graphical and numerical analysis tools. Level 3 (gridded) data is the common form in which large data sets of this type are distributed for scientific analysis. We find that Level 3 data is inadequate for the data comparisons required for validation. Level 2 data (individual measurements in geophysical units) is needed. A sampling problem arises when individual measurements, which are not uniformly distributed in space or time, are used for the comparisons. Standard 'interpolation' methods involve fitting the measurements for each data set to surfaces, which are then compared. We are experimenting with formal criteria for selecting geographical regions, based upon the spatial frequency and variability of measurements, that allow us to quantify the uncertainty due to sampling. As part of this project, we are also dealing with ways to keep track of constraints placed on the output by assumptions made in the computer code. The need to work with Level 2 data introduces a number of other data handling issues, such as accessing data files across machine types, meeting large data storage requirements, accessing other validated data sets, processing speed and throughput for interactive graphical work, and problems relating to graphical interfaces.

Kahn, Ralph↗

Fire Station #2, Former Sewage Treatment Plant #17, and Towway Area-SWMU 114 PFAS Site Assessment Progress Report Kennedy Space Center, Florida

This PFAS Site Assessment Progress Report (SAPR) presents the findings of the 2022 PFAS investigation conducted from November 2021 through August 2022 at Solid Waste Management Unit (SWMU) 114 located within Kennedy Space Center (KSC), Florida. SWMU 114 includes area around Fire Station #2, Former Sewage Treatment Plant #17, the southern portion of the Shuttle Landing Facility Runway, Remote Launch Vehicle Hangar, and the Towway area. Fire Station #2 was constructed in 2008 and is currently active, housing fire station personnel and equipment, including aqueous film forming foam (AFFF). Releases of AFFF has occurred at SWMU 114. Previous environmental assessments have been performed at SWMU 114, including soil, groundwater, and surface water sampling for volatile organic compounds, polycyclic aromatic hydrocarbons, total petroleum hydrocarbons, and metals. No active remediation has been performed at the SWMU 114. PFAS site assessment field activities were conducted at SWMU 114 from November 2021 through August 2022. During the 2021-2022 Site Assessment, 124 direct-push samples were collected from 27 locations, 17 surface water samples were collected from 15 locations, 41 groundwater samples were collected from 37 newly installed monitoring wells, five concrete samples were collected from four locations, and one asphalt sample was collected. Additionally, two soil borings were advanced to 60 feet for lithologic descriptions, ten staff gauges were installed, and one round of water level measurements were collected from monitoring wells and staff gauges for groundwater flow determination. All groundwater and surface water samples were analyzed for 25 PFAS analytes by USEPA Method 537M. Concrete, and asphalt samples were analyzed by synthetic precipitation leaching procedure (SPLP) PFAS analysis by USEPA Modified Method 537M. Groundwater results were compared to the most recent Regional Screening Levels (RSLs) published by USEPA for residential tap water (USEPA, 2022a) to determine the extent of PFAS contamination at SWMU 114 for six PFAS analytes (PFOA, PFNA, PFBS, PFHxS, PFOS, and GenX). Surface water results were compared to the FDEP surface water screening levels (SW SLs) (FDEP, 2020) for PFOA and PFOS. The PFAS investigation concluded that groundwater exceeding RSLs extends east and south to Banana Creek and west to approximately the center of the SLF runway. The extent of PFAS is approximated to the north, to an area between Sharkey Road and Astronaut Road, where samples below the RSLs do not fully bound SWMU 114. At least two distinct PFAS source areas are located near Fire Station #2 and along Towway, at S114-MW0007S, within SWMU 114. Groundwater head measurements indicate that flow at SWMU 114 is generally similar across the shallow and intermediate water tables. A northeast to southwest trending groundwater divide is located near the middle of Towway where groundwater southeast of the divide flows to the south and groundwater northwest of the divide flows to the west. The groundwater divide generally separates the two areas of higher PFAS concentrations. Surface water samples indicated concentrations of PFOS above the SW SLs in surface water bodies across the site. Further assessment and sampling are required to better understand the interaction between groundwater and surface water at SWMU 114. Concrete and asphalt samples collected confirm that a significant release of AFFF occurred near the stormwater pond northwest of Fire Station #2. Additional concrete samples surrounding Fire Station #2 and at the northwest and southeast edges of the SLF tarmac indicate elevated PFOS concentrations. These results indicate that discharges of AFFF in these locations have infiltrated into asphalt and concrete and may act as a continuing source of PFAS to groundwater and surface water after rain events. Additional direct-push samples are required to delineate PFAS at SWMU 114. Samples may need to extend beyond the Former SLF Rescue Building and Morpheous Test Site to delineate PFAS in groundwater. Monitoring wells should be sampled and gauged quarterly to determine if seasonal impacts are observable, especially in shallow wells near surface water features. Furthermore, surface water samples should be collected from additional ditches to further define the extent of surface water impacts at SWMU 114 and extending along the SLF runway. Staff gauges should be gauged quarterly with groundwater gauging to determine surface water flow and interaction with groundwater. The PFAS sampling results and path forward for SWMU 114 were presented to the KSC Remediation Team in October 2022. Once the PFAS SAPR is approved, it will be submitted to the Florida Department of Environmental Protection.

Howard Franklin Fowler↗

Development and Design Application of Rigidized Surface Insulation Thermal Protection Systems, Volume 1

Materials and design technology of the all-silica LI-900 rigid surface insulation (RSI) thermal protection system (TPS) concept for the shuttle spacecraft is presented. All results of contract development efforts are documented. Engineering design and analysis of RSI strain arrestor plate material selections, sizing, and weight studies are reported. A shuttle prototype test panel was designed, analyzed, fabricated, and delivered. Thermophysical and mechanical properties of LI-900 were experimentally established and reported. Environmental tests, including simulations of shuttle loads represented by thermal response, turbulent duct, convective cycling, and chemical tolerance tests are described and results reported. Descriptions of material test samples and panels fabricated for testing are included. Descriptions of analytical sizing and design procedures are presented in a manner formulated to allow competent engineering organizations to perform rational design studies. Results of parametric studies involving material and system variables are reported. Material performance and design data are also delineated.

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Microwave Photoelasticity: Exploiting Multiple Resonances to Measure Stress Changes within Yttria-Partially-Stabilized-Zirconia

The NASA Glenn Research Center is developing non-destructive-testing (NDT) methods to enable the measurement of stresses embedded in optically opaque materials using microwave radiation in a free-space quasi-optical system. This methodology tracks microwave resonances observed in reflected scattering parameters extracted from materials under load. In this paper, we report the successful measurement of the stress-optic-coefficient of bulk yttria-partially stabilized zirconia (YTZP) ceramic of C = 1.42 x 10-4 ± 6.65 x 10-6 (1/GPa), across W-Band (80-100 GHz), and determined that this result is independent of sample thickness. The primary goal of this research is to establish a methodology to quantify and assess the life expectancy of ceramic thermal and environmental barrier coating (TBCs/EBCs). Bulk YTZP samples can undergo multiple resonances within a contiguous measurement bandwidth, each corresponding to an integer multiple wave number ∝. This allows for the acquisition and analysis of multiple stress measurement points within a single sample. As an additional benefit, one can approximate the refractive index of YTZP across a wide bandwidth by observing multiple resonances produced by a set of samples with varying thicknesses. Using this approach, the refractive index of bulk YTZP was found to be n = 5.80 ± 0.043 across the 85-115 GHz frequency band.

Seth W. Waldstein↗

One Year in the Extreme Isolation of Antarctica—Is This Enough to Modulate an “Allergic” Sensitization?

(1) Background: After spending a year wintering in Antarctica, individual expedition members have reported increased or even new allergic reactions to environmental allergens after their return. (2) Methods: Blood samples from five overwintering crews were analyzed using the chip based multiplex ALEX Allergy Explorer (MacroArray Diagnostics GmbH, Austria). (3) Results: About one third of the 39 participants displayed specific IgEs against pollen. In most individuals, kinetics showed a reduction in the specific IgE at the time about nine months after deployment to Antarctica. Five participants had the highest specific IgE levels after returning to the “normal” world. The examination of the specific IgE relative to house dust mites and storage mites showed different kinetics. Six out of 10 had the highest specific IgE concentrations at the inner Antarctic measurement time point. These data corresponded well to the general situation in the stations. At the stations themselves, there were almost no pollen particle load, especially at Concordia. (4) Conclusions: Antarctic long-term confinement can induce an altered immune function, which is in some individuals pronounced after return to the familiar allergen environment. Future prospective studies in larger cohorts are needed to further specify these first results.

Matthias Feuerecker↗

Reanalyzing Environmental Lidar Data for Archaeology: Mesoamerican Applications and Implications

This paper presents a preliminary archaeological assessment of extensive transects of lidar recently collected by environmental scientists over southern Mexico using the G-LiHT system of NASA's Goddard Space Flight Center. In particular, this article offers the results of a first phase of research, consisting of: 1) characterization and classification of the cultural and ecological context of the samples, and 2) bare earth processing and visual inspection of a sample of the flight paths for identification of probable anthropogenic Precolumbian features. These initial results demonstrate that significant contributions to understanding variations in Precolumbian land-use and settlement patterns and change is possible with truly multi-regional lidar surveys not originally captured for archaeological prospection. We point to future directions for the development of archaeological applications of this robust data set. Finally, we offer the potential for enriching archaeological research through tightly coupled collaborations with environmental science and monitoring. Archaeologists in the neotropics can acquire more data, better realize the full potential of lidar surveys, and better contribute to interdisciplinary studies of human-environmental dynamic systems through regionally focused and collaborative scientific research.

Golden, Charles↗

Global atmospheric distribution and trend of methylchloroform /CH3CCl3/

Results of global measurements of the concentration of atmospheric methylchloroform, a man-made gas with potentially harmful environmental consequences, performed over a two-year period are presented. Samples were collected weekly at Pt. Barrow and Poker Flats, Alaska, Cape Meares, Oregon, Cape Kumakahi, Hawaii, Samoa, and Cape Grim, Tasmania, and yearly at the South Pole, and methylchloroform concentrations were determined by electron capture-gas chromatographic techniques. A latitudinal profile of CH3CCl3 concentrations derived from the data exhibits a bump at high northern latitudes, where most of the sources are located. Average concentrations calculated for the Northern and Southern Hemispheres showed a rise in global concentrations at a rate of 6.7 + or - 2.0%/year for the period from January 1979 to January 1981, with concentrations rising more slowly in 1980 than in 1979. These yearly increases are also smaller than earlier rates of increase, explainable by a reduction in the rate of emission increase, and are consistent with an atmospheric lifetime of between 6 and 10 years.

Rasmussen, R. A.↗

Relative effectiveness of kinetic analysis vs single point readings for classifying environmental samples based on community-level physiological profiles (CLPP)

The relative effectiveness of average-well-color-development-normalized single-point absorbance readings (AWCD) vs the kinetic parameters mu(m), lambda, A, and integral (AREA) of the modified Gompertz equation fit to the color development curve resulting from reduction of a redox sensitive dye from microbial respiration of 95 separate sole carbon sources in microplate wells was compared for a dilution series of rhizosphere samples from hydroponically grown wheat and potato ranging in inoculum densities of 1 x 10(4)-4 x 10(6) cells ml-1. Patterns generated with each parameter were analyzed using principal component analysis (PCA) and discriminant function analysis (DFA) to test relative resolving power. Samples of equivalent cell density (undiluted samples) were correctly classified by rhizosphere type for all parameters based on DFA analysis of the first five PC scores. Analysis of undiluted and 1:4 diluted samples resulted in misclassification of at least two of the wheat samples for all parameters except the AWCD normalized (0.50 abs. units) data, and analysis of undiluted, 1:4, and 1:16 diluted samples resulted in misclassification for all parameter types. Ordination of samples along the first principal component (PC) was correlated to inoculum density in analyses performed on all of the kinetic parameters, but no such influence was seen for AWCD-derived results. The carbon sources responsible for classification differed among the variable types with the exception of AREA and A, which were strongly correlated. These results indicate that the use of kinetic parameters for pattern analysis in CLPP may provide some additional information, but only if the influence of inoculum density is carefully considered. c2001 Elsevier Science Ltd. All rights reserved.

NASA Center KSC↗

Coatings for Oxidation and Hot Corrosion Protection of Disk Alloys

Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can potentially seriously degrade the life of the disk. Application of metallic coatings are one means of protecting disk alloys from this environmental attack. However, simply the presence of a metallic coating, even without environmental exposure, can degrade the LCF life of a disk alloy. Therefore, coatings must be designed which are not only resistant to oxidation and corrosion attack, but must not significantly degrade the LCF life of the alloy. Three different Ni-Cr coating compositions (29, 35.5, 45wt. Cr) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One coating also received a thin ZrO2 overcoat. The coated samples were also given a short oxidation exposure in a low PO2 environment to encourage chromia scale formation. Without further environmental exposure, the LCF life of the coated samples, evaluated at 760C, was less than that of uncoated samples. Hence, application of the coating alone degraded the LCF life of the disk alloy. Since shot peening is commonly employed to improve LCF life, the effect of shot peening the coated and uncoated surface was also evaluated. For all cases, shot peening improved the LCF life of the coated samples. Coated and uncoated samples were shot peened and given environmental exposures consisting of 500 hrs of oxidation followed by 50 hrs of hot corrosion, both at 760C). The high-Cr coating showed the best LCF life after the environmental exposures. Results of the LCF testing and post-test characterization of the various coatings will be presented and future research directions discussed.

LCF life↗

Development of Computational Environmental Microbiome Workflows for the Laboratory and the International Space Station

Identification of microorganisms in the spaceflight environment is critical for crew health risk assessment on the International Space Station (ISS). Since 2017, nanopore sequencing technology has been used to support thein situ identification of microbial species during spaceflight. Beginning in 2018, a culture-independent, swab-to-sequencer method was implemented onboard the ISS to provide a more thorough insight of the ISS microbiome. Eliminating microbial culture enables identification of difficult-to-culture organisms, reduces risks associated with potentially pathogenic cultures, and could significantly reduce the time from sample-to-answer. However, this molecular-based approach generates large metagenomic datasets that require substantial computational resources for analysis. To process nanopore-generated sequencing data, the JSC Microbiology Laboratory established a bioinformatics workflow on Amazon EC2 under the security guidance of the NASA Science Managed Cloud Environment (SMCE).This resource allows for the development, testing, and accessing of computational tools for processing large and complex datasets. The work described here will address the downlinking of data from the ISS, the automated pipeline developed to identify targeted bacterial and fungal organisms, and the time from sampling onboard to microbial identification. The pipelines have been enhanced to address high and low biomass samples using optimization based on sample source (air, water, or surface) and type of collection (filter, colony, or swab).The resulting microbiome data can be assessed beyond microbial identifications to gain understanding toward population changes over time, potential selective environmental pressures, and evaluating correlations with a wide range of additional data sets. Metagenome analysis pipelines in development could allow for simultaneous identification of microbial species, gene function, and gene pathways present in the environment. Beyond the ground processing, the developed analysis pipeline is currently deployed onboard the ISS to allow for near real-time assessments of the ISS microbiome. This study serves as a critical foundation for exploration missions, where rapid microbiome analyses will be required.

G. Marie Sharp↗

Studies in remote sensing of Southern California and related environments

A summary is presented of the research activities in southern California to determine whether meaningful geographic information was obtainable by use of remote sensing in an area already well documented or if the techniques and methodology could be transferred to related environments. Several broad characteristics of the regional geography were investigated with regards to their feasibility to be studied by aircraft and spacecraft sensors to improve the inventory and understanding of resources and environmental circumstances and to serve as models for future geographic analysis of other regions when using remote sensing devices. Sample activities are described in detail and three experiments producing worthwhile results are highlighted: mapping montane vegetation with color IR imagery, analysis of urban residual environment using color IR aerial photography, and regional agricultural land use mapping tested against color IR photography.

Bowden, L. W.↗

Launch Complex 39A, SWMU 008 2023 Long-Term Monitoring Report Kennedy Space Center, Florida

The 2023 Long-Term Monitoring (LTM) Report (LTMR) presents the annual and semi-annual groundwater monitoring results for Launch Complex 39A (LC39A), Solid Waste Management Unit (SWMU) 008, at Kennedy Space Center (KSC), Florida. The reporting period covered under this LTMR is from January to December 2023, and represents the first year of site-wide monitoring following Air Sparge (AS) system shutdown at the end of 2022. AS system operation at LC39A began operation in 2015. The AS system consisted of a total of 173 AS wells ranging in depth from 11 to 37 feet below land surface. The overall remedial objective for the AS Interim Measure was to actively decrease concentrations of COCs to less than their respective Florida Department of Environmental Protection Natural Attenuation Default Concentrations, so that LC39A can transition into an LTM program. This objective was achieved in 2022, with 2023 marking Year 1 of the LTM program to monitor the residual groundwater plume. VOC results indicate that COC concentrations have continued to decrease or stabilize, with no rebound observed since AS system shutdown. Vinyl chloride was the only COC detected above its GCTL, with the highest concentration detected at 8.0 μg/L. PFAS results detected 15 different PFAS compounds (out of 32 analyzed) between the six monitoring wells sampled. Two PFAS compounds, perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), currently have FDEP Provisional GCTLs of 70 nanograms per liter (ng/L). PFOS was detected in one of the six samples above the FDEP Provisional GCTL at a concentration of 200 ng/L. PFOA was not detected above the FDEP Provisional GCTL in any of the six samples. PFOS and PFOA also currently have United States Environmental Protection Agency (USEPA) Maximum Contaminant Levels (MCLs) of 4 ng/L. PFOS was detected in all six samples above the USEPA MCL. PFOA was detected in three of the six samples above the USEPA MCL. Three other PFAS compounds, perfluorohexanesulfonic acid (PFHxS), perfluoro-n-nonanoic acid (PFNA), and hexafluoropropylene oxide dimer acid (GenX), currently have USEPA MCLs of 10 ng/L. PFHxS, PFNA, and GenX were not detected at concentrations greater than their respective USEPA MCLs in any of the six wells. Additional PFAS sampling will occur as part of a PFAS Site Assessment to be conducted in the future. Based on Year 1 LC39A LTM results, recommendations for 2024 are to continue with the second year of LTM in 2024 with the same monitoring well network as Year 1 (18 wells). The three wells that were on a semi-annual schedule will transition to an annual schedule to align with the remaining wells. The next annual event is scheduled for May 2024. The three wells that were found to be inadvertently destroyed will be properly abandoned and a replacement well in the vicinity of former monitoring well 21ST-MW0030I will be installed. This new well will be added to the LTM sampling plan upon installation.

Deborah M. Wilson↗

JSC Advanced Curation: Research and Development for Current Collections and Future Sample Return Mission Demands

Curation of NASA's astromaterials sample collections is a demanding and evolving activity that supports valuable science from NASA missions for generations, long after the samples are returned to Earth. For example, NASA continues to loan hundreds of Apollo program samples to investigators every year and those samples are often analyzed using instruments that did not exist at the time of the Apollo missions themselves. The samples are curated in a manner that minimizes overall contamination, enabling clean, new high-sensitivity measurements and new science results over 40 years after their return to Earth. As our exploration of the Solar System progresses, upcoming and future NASA sample return missions will return new samples with stringent contamination control, sample environmental control, and Planetary Protection requirements. Therefore, an essential element of a healthy astromaterials curation program is a research and development (R&D) effort that characterizes and employs new technologies to maintain current collections and enable new missions - an Advanced Curation effort. JSC's Astromaterials Acquisition & Curation Office is continually performing Advanced Curation research, identifying and defining knowledge gaps about research, development, and validation/verification topics that are critical to support current and future NASA astromaterials sample collections. The following are highlighted knowledge gaps and research opportunities.

Fries, M. D.↗

A modular approach for automated sample preparation and chemical analysis

Changes in international relations, especially within the past several years, have dramatically affected the programmatic thrusts of the U.S. Department of Energy (DOE). The DOE now is addressing the environmental cleanup required as a result of 50 years of nuclear arms research and production. One major obstacle in the remediation of these areas is the chemical determination of potentially contaminated material using currently acceptable practices. Process bottlenecks and exposure to hazardous conditions pose problems for the DOE. One proposed solution is the application of modular automated chemistry using Standard Laboratory Modules (SLM) to perform Standard Analysis Methods (SAM). The Contaminant Analysis Automation (CAA) Program has developed standards and prototype equipment that will accelerate the development of modular chemistry technology and is transferring this technology to private industry.

Clark, Michael L.↗

SRB Materials and Processes Assessment from Laboratory and Ocean Environmental Tests

The Materials and Processes Laboratory evaluation of Solid Rocket Boosters (SRB) and Solid Rocket Motors (SRM) candidate material, both in-house and with ocean exposure tests at Panama City and Kennedy Space Center (KSC), Florida is presented. Early sample tests showed excellent seawater corrosion resistance for inconel 718 and titanium 6A1-4V alloys. Considerable corrosion and biofouling occurred with bare 2219-T87 aluminum. Subsequent tests conclusively demonstrated that epoxy coatings prevented corrosion of 2219-T87 aluminum as long as the coatings stays intact. The results and assessment of the series of ocean environmental tests that were conducted are also presented.

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